BEIRUT (AP) — U.S.-backed Syrian fighters are battling the Islamic State group in eastern Syria 10 days after declaring victory over the extremists, an official with the Kurdish-led force said Tuesday.

Mustafa Bali, a spokesman for the Syrian Democratic Forces, said they are rooting out groups of militants who were hiding in caves in and near the village of Baghouz. He added that SDF experts are still removing mines and booby-traps in areas liberated in recent weeks.

The SDF declared military victory over IS on March 23 after liberating what it said was the last pocket of territory held by the militants. The victory marked the end of the brutal self-styled caliphate the group carved out in large parts of Iraq and Syria in 2014.

The nearly five-year war left a swath of destruction across both countries and ended in Baghouz, a tiny village near the Iraqi border where the cornered militants made their last stand, under a grueling siege for weeks.

The Britain-based Syrian Observatory for Human Rights said the U.S.-led coalition is still conducting airstrikes against IS. It says senior IS commanders and prisoners held by the extremists are believed to be in the caves on the east bank of the Euphrates River.

The Observatory, which closely monitors the Syrian war through contacts on the ground, says scores of IS fighters and commanders who refused to surrender are still in the area.

During the last weeks of fighting in Baghouz, thousands of civilians, IS fighters and their families were evacuated. Many were moved to al-Hol, a camp for the displaced in northeastern Syria, which now holds 70,000 people.

An aid group said 31 deaths were recorded in the final week of March among people making their way out of Baghouz and toward the camp.

The International Rescue Committee said the highest weekly death rate reflected the desperate conditions endured by those who left, mostly women and children. It said a total of 217 people died while evacuating Baghouz in the final weeks of the battle. Most were toddlers suffering from malnutrition.